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EP0573029A2 - Use of refractory, oxide micropowder for making ceramic masses and bodies - Google Patents

Use of refractory, oxide micropowder for making ceramic masses and bodies Download PDF

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Publication number
EP0573029A2
EP0573029A2 EP93108918A EP93108918A EP0573029A2 EP 0573029 A2 EP0573029 A2 EP 0573029A2 EP 93108918 A EP93108918 A EP 93108918A EP 93108918 A EP93108918 A EP 93108918A EP 0573029 A2 EP0573029 A2 EP 0573029A2
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Prior art keywords
micropowder
proviso
use according
matrix material
ceramic matrix
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EP93108918A
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German (de)
French (fr)
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EP0573029A3 (en
EP0573029B1 (en
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Roland Dr. Dipl.-Ing. Heindl
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Veitsch Radex GmbH and Co OG
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Veitsch Radex GmbH and Co OG
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
    • C04B35/63—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B using additives specially adapted for forming the products, e.g.. binder binders
    • C04B35/6303—Inorganic additives
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics

Definitions

  • the invention relates to the use of a finely divided magnesium oxide micropowder for the production of ceramic masses and moldings.
  • AT 392 464 B discloses a magnesium oxide in the form of a fine powder and its use for the production of high-density ceramics.
  • the finely divided magnesium oxide has a particle size ⁇ 15 ⁇ m and a specific surface area ⁇ 20 m2 / g (determined according to BET from the nitrogen adsorption isotherm). It is further characterized by a grain shape factor of the primary particles between 1 and 1.5 and a coating of a hydrophobizing substance.
  • the grain shape factor mentioned essentially describes spherical particles, the degree of dispersion of which is increased by the addition of a hydrophobizing substance.
  • a finely divided magnesium oxide powder which is obtained from an aqueous suspension by spray drying, the suspension receiving a coating agent which is to be deposited in the monomolecular layer as possible on the surface of the oxide particles.
  • the coating agent consists, for example, of a carboxylic acid. Due to the preparation in an aqueous suspension, however, hydration of the magnesium oxide to magnesium hydroxide cannot be avoided, although the degree of hydration can be limited to values below 10% by weight by using the coating agent and the subsequent spray drying. However, hydration results in a change (enlargement) of the particle shape that is undesirable.
  • a degree of hydration of 1.0% by weight linearly increases the corresponding grain by 1.0%.
  • the known fine-particle magnesium oxide powders can only be processed together with binders in a heavy ceramic matrix.
  • the invention has for its object to show a way with which refractory ceramic masses and moldings can be produced, which lead to sufficient green stability and high density after the fire even without complex preparation of the starting components.
  • the invention is based on the knowledge that this can be achieved by using a finely divided, refractory, oxidic micropowder in a coarse-ceramic refractory matrix, the micropowder being largely in the form of a single grain.
  • the use of the finely divided oxidic micropowder with a largely uniform grain diameter leads to physical adhesion of the particles to one another even in the green state, which continues in the course of the fire in a uniform sintering.
  • the finely divided component advantageously fills the gusset between the coarser particles in the form of a densest spherical packing and thus enables the finished (fired) product to have a significantly reduced porosity.
  • the invention in its most general embodiment relates to the use of a finely divided, refractory, oxidic micropowder obtained after dispersion in a non-aqueous dispersion medium, largely of a uniform grain size in a coarse-ceramic, refractory matrix material for the production of ceramic masses and moldings of high green strength and high density after a fire.
  • micropowder should be used in a particle size of less than 10 ⁇ m, particle sizes below 1 ⁇ m being particularly advantageous in the sense of the invention.
  • single grain or “largely uniform grain size” are not to be understood in the sense that an exact single grain is used because this can only be produced with increased effort, although it would be particularly preferred; to this extent, according to one embodiment variant, the use of a finely divided micropowder is proposed, in which 90% by weight of the particles have a maximum deviation from the mean particle diameter of ⁇ 10%.
  • micropowder used can vary depending on the application, but should in principle be in the order of 5 to 18% by weight, based on the total mass, a proportion of 10 to 15% by weight being likely for most applications.
  • the corresponding mass fraction is previously prepared in a non-aqueous dispersing medium (which prevents hydration in the case of hydration-sensitive oxides such as MgO), whereby the dispersing medium which is inert with respect to the solid can consist, for example, of naphthenic oils or fatty alcohols and a modified alkyd resin (polyester) is used as the dispersant, for example.
  • a non-aqueous dispersing medium which prevents hydration in the case of hydration-sensitive oxides such as MgO
  • the dispersing medium which is inert with respect to the solid can consist, for example, of naphthenic oils or fatty alcohols and a modified alkyd resin (polyester) is used as the dispersant, for example.
  • the refractory oxidic micropowder can consist of different oxides, for example MgO, Al2O3, Cr2O3 and / or TiO2.
  • the oxidic micropowder can consist of only one of these oxides; however, it is also possible to use mixtures of these oxides as micropowder, in particular when spinel formation is desired. In this case, it makes sense to use a MgO / Cr2O3 dispersion, for example.
  • Dispersions are understood to mean which have a solids content of over 85% by weight, based on the total dispersion. The proportion of the disperser is then up to 15% by weight.
  • the coarse ceramic matrix material is selected depending on the desired material properties.
  • the micropowder can also consist, for example, of a spinel-forming MgO / Cr2O3 or MgO / Al2O3 dispersion.
  • Al2O3 for example alumina, tabular alumina, corundum
  • the use of an Al2O3 micropowder offers itself, which, however, can be replaced in whole or in part by TiO2 or another refractory oxidic micropowder.
  • this should preferably be processed in a non-aqueous dispersion medium in order to keep the water content of the processed mass as low as possible.
  • the processing technology with a non-aqueous Dispersing medium has the advantage that the above-mentioned unusually high solid concentrations of the dispersion can be achieved more easily, with the result that in this way not only the green stability of the ceramic mass (after mixing with the coarse ceramic matrix material) but also the density the fire can be significantly promoted.
  • micropowder can then also be used in aqueous systems.
  • a further significant advantage is that the molded parts produced from the composition described are not subject to any significant shrinkage in the fire.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Compositions Of Oxide Ceramics (AREA)
  • Ceramic Products (AREA)

Abstract

The invention relates to the use of a finely disperse magnesium oxide micropowder for the preparation of ceramic masses and mouldings.

Description

Die Erfindung betrifft die Verwendung eines feinteiligen Magnesiumoxid-Mikropulvers zur Herstellung von keramischen Massen und Formteilen.The invention relates to the use of a finely divided magnesium oxide micropowder for the production of ceramic masses and moldings.

Aus der AT 392 464 B ist ein Magnesiumoxid in Form eines feinen Pulvers und seine Verwendung zur Herstellung hochdichter Keramiken bekannt. Das feinteilige Magnesiumoxid weist eine Teilchengröße < 15 µm und eine spezifische Oberfläche < 20 m²/g (bestimmt nach BET aus der Stickstoffadsorptionsisotherme) auf. Es ist weiter durch einen Kornformfaktor der Primärteilchen zwischen 1 und 1,5 sowie eine Beschichtung aus einer hydrophobierenden Substanz gekennzeichnet Der genannte Kornformfaktor beschreibt im wesentlichen kugelförmige Teilchen, deren Dispergierungsgrad durch den genannten Zusatz einer hydrophobierenden Substanz erhöht wird.AT 392 464 B discloses a magnesium oxide in the form of a fine powder and its use for the production of high-density ceramics. The finely divided magnesium oxide has a particle size <15 μm and a specific surface area <20 m² / g (determined according to BET from the nitrogen adsorption isotherm). It is further characterized by a grain shape factor of the primary particles between 1 and 1.5 and a coating of a hydrophobizing substance. The grain shape factor mentioned essentially describes spherical particles, the degree of dispersion of which is increased by the addition of a hydrophobizing substance.

Durch die Hydrophobierung werden zwar (unerwünschte) Agglomerate teilweise verhindert, letztendlich kommt es beim Brand jedoch zu einer Sammelkristallisation und damit zu einem Wachstum der feinteiligen MgO-Teilchen, das in einem unregelmäßigen Gefügeaufbau resultiert. Aus der Praxis ist weiter ein feinteiliges Magnesiumoxidpulver bekannt, das aus einer wässrigen Suspension durch Sprühtrocknen erhalten wird, wobei die Suspension ein Beschichtungsmittel erhält, das sich in möglichst monomolekularer Schicht auf der Oberfläche der Oxidteilchen niederschlagen soll. Das Beschichtungsmittel besteht dabei zum Beispiel aus einer Carbonsäure. Aufgrund der Aufbereitung in einer wässrigen Suspension läßt sich jedoch eine Hydratation des Magnesiumoxids zu Magnesiumhydroxid nicht vermeiden, wenngleich der Hydratationsgrad durch die Verwendung des Beschichtungsmittels und die anschließende Sprühtrocknung auf Werte unter 10 Gew.-% beschränkt werden kann. Die Hydratation hat jedoch eine Veränderung (Vergrößerung) der Teilchenform zur Folge, die unerwünscht ist. Als Richtwert kann angegeben werden, daß ein Hydratationsgrad von 1,0 Gew.-% das entsprechende Korn um 1,0 % linear vergrößert.Although the hydrophobization partially prevents (unwanted) agglomerates, ultimately there is a collective crystallization during the fire and thus a growth of the fine-particle MgO particles, which results in an irregular structure. In practice, a finely divided magnesium oxide powder is also known which is obtained from an aqueous suspension by spray drying, the suspension receiving a coating agent which is to be deposited in the monomolecular layer as possible on the surface of the oxide particles. The coating agent consists, for example, of a carboxylic acid. Due to the preparation in an aqueous suspension, however, hydration of the magnesium oxide to magnesium hydroxide cannot be avoided, although the degree of hydration can be limited to values below 10% by weight by using the coating agent and the subsequent spray drying. However, hydration results in a change (enlargement) of the particle shape that is undesirable. As a guideline, it can be stated that a degree of hydration of 1.0% by weight linearly increases the corresponding grain by 1.0%.

Es kommt hinzu, daß sich die bekannten feinteiligen Magnesiumoxidpulver nur zusammen mit Bindemitteln in einer grobkeramischen Matrix verarbeiten lassen.In addition, the known fine-particle magnesium oxide powders can only be processed together with binders in a heavy ceramic matrix.

Der Erfindung liegt die Aufgabe zugrunde, eine Möglichkeit aufzuzeigen, mit der sich feuerfeste keramische Massen und Formteile herstellen lassen, die auch ohne aufwendige Aufbereitung der Ausgangsbestandteile zu einer ausreichenden Grünstandsfestigkeit und hohen Dichte nach dem Brand führen.The invention has for its object to show a way with which refractory ceramic masses and moldings can be produced, which lead to sufficient green stability and high density after the fire even without complex preparation of the starting components.

Dabei liegt der Erfindung die Erkenntnis zugrunde, daß dies durch die Verwendung eines feinteiligen, feuerfesten, oxidischen Mikropulvers in einer grobkeramischen feuerfesten Matrix erreicht werden kann, wobei das Mikropulver weitestgehend in Form eines Einkorns vorliegt.The invention is based on the knowledge that this can be achieved by using a finely divided, refractory, oxidic micropowder in a coarse-ceramic refractory matrix, the micropowder being largely in the form of a single grain.

Es hat sich nämlich gezeigt, daß bei Verwendung eines derartigen Einkorns eine rein physikalische Bindung zwischen den Teilchen erreicht werden kann, die selbst im Grünzustand bereits zu einer ausreichenden und zum Teil gegenüber dem Stand der Technik erhöhten Grundfestigkeit führt. Durch die Verwendung eines Einkorns wird außerdem in vorteilhafter Weise eine Sammelkristallisation verhindert, bei der kleinere Teilchen bei der Sinterung mit größeren Teilchen koagulieren, wodurch eine unregelmäßige Sintercharakteristik entsteht.It has been shown that when such a grain is used, a purely physical bond between the particles can be achieved, which even in the green state leads to a sufficient basic strength, which is sometimes higher than in the prior art. The use of a single grain also advantageously prevents collective crystallization, in which smaller particles coagulate with larger particles during sintering, which results in an irregular sintering characteristic.

Die Verwendung des feinteiligen oxidischen Mikropulvers mit weitestgehend einheitlichem Korndurchmesser führt dagegen bereits im Grünzustand zu einer physikalischen Haftung der Teilchen untereinander, die sich beim Brand in einer gleichmäßigen Sinterung fortsetzt. Die feinteilige Komponente füllt dabei in vorteilhafter Weise die Zwickel zwischen den gröberen Teilchen in Form einer dichtesten Kugelpackung aus und ermöglicht so am fertigen (gebrannten) Produkt eine deutlich verringerte Porosität.In contrast, the use of the finely divided oxidic micropowder with a largely uniform grain diameter leads to physical adhesion of the particles to one another even in the green state, which continues in the course of the fire in a uniform sintering. The finely divided component advantageously fills the gusset between the coarser particles in the form of a densest spherical packing and thus enables the finished (fired) product to have a significantly reduced porosity.

Statistisch kann berechnet werden, daß beispielsweise bei einer Ausgangsporosität von 20 Vol.-% im Grobkorn-Matrixmaterial (mit einer maximalen Korngröße von 3 mm und einer minimalen Korngröße über der des Feinkornanteils) sowie Zugabe von 15 Gew.-% des feinteiligen Einkorn-Oxid-Pulvers mit einer Korngröße von etwas unter 1,0 µm eine Restporosität von 8 bis 10 Vol.-% am fertigen (gebrannten) Produkt gegeben ist.Statistically it can be calculated that, for example, with an initial porosity of 20% by volume in the coarse-grain matrix material (with a maximum grain size of 3 mm and a minimum grain size above that of the fine-grain fraction) and addition of 15% by weight of the finely divided single-grain oxide Powder with a grain size of slightly less than 1.0 µm There is a residual porosity of 8 to 10% by volume of the finished (fired) product.

Dies vorausgeschickt betrifft die Erfindung in ihrer allgemeinsten Ausführungsform die Verwendung eines nach Dispergierung in einem nicht wässrigen Dispergiermedium erhaltenen feinteiligen, feuerfesten, oxidischen Mikropulvers weitestgehend einheitlicher Korngröße in einem grobkeramischen feuerfesten Matrixmaterial zur Herstellung von keramischen Massen und Formteilen hoher Grünstandsfestigkeit und hoher Dichte nach einem Brand.That being said, the invention in its most general embodiment relates to the use of a finely divided, refractory, oxidic micropowder obtained after dispersion in a non-aqueous dispersion medium, largely of a uniform grain size in a coarse-ceramic, refractory matrix material for the production of ceramic masses and moldings of high green strength and high density after a fire.

Das Mikropulver sollte dabei in einer Teilchengröße von weniger als 10 µm eingesetzt werden, wobei Teilchengrößen unter 1 µm besonders günstig im erfindungsgemäßen Sinne wirken.The micropowder should be used in a particle size of less than 10 μm, particle sizes below 1 μm being particularly advantageous in the sense of the invention.

Die Begriffe "Einkorn" beziehungsweise "weitestgehend einheitliche Korngröße" sind aber nicht in dem Sinne zu verstehen, daß ein exaktes Einkorn eingesetzt wird, weil dieses nur mit erhöhtem Aufwand überhaupt herstellbar, wenngleich besonders bevorzugt wäre; insoweit wird nach einer Ausführungsvariante die Verwendung eines feinteiligen Mikropulvers vorgeschlagen, bei dem 90 Gew.-% der Teilchen ein maximale Abweichung vom mittleren Teilchendurchmesser von ± 10 % aufweisen.However, the terms "single grain" or "largely uniform grain size" are not to be understood in the sense that an exact single grain is used because this can only be produced with increased effort, although it would be particularly preferred; to this extent, according to one embodiment variant, the use of a finely divided micropowder is proposed, in which 90% by weight of the particles have a maximum deviation from the mean particle diameter of ± 10%.

Die verwendete Menge des Mikropulvers kann anwendungsspezifisch variieren, sollte aber grundsätzlich in der Größenordnung zwischen 5 und 18 Gew.-%, bezogen auf die Gesamtmasse, liegen, wobei ein Anteil von 10 bis 15 Gew.-% für die meisten Anwendungsbereiche infrage kommen dürfte.The amount of micropowder used can vary depending on the application, but should in principle be in the order of 5 to 18% by weight, based on the total mass, a proportion of 10 to 15% by weight being likely for most applications.

Beim grobkeramischen Matrixmaterial kann auf konventionelle Siebkennlinien zurückgegriffen werden, die im Kornbereich < 5 mm und > als das Mikropulver vorliegen.In the case of coarse ceramic matrix material, conventional sieving characteristics can be used which are in the grain area <5 mm and> as the micropowder.

Wie bereits eingangs erläutert, besteht ein wesentlicher Vorteil der beschriebenen Verwendung darin, daß aus der Kombination von grobkeramischem Matrixmaterial und dispergiertem feinteiligen Mikropulver die Möglichkeit resultiert, bindemittelfrei zu arbeiten, da die feinteilige Einkorn-Komponente quasi als "in-situ-Bindemittel" wirkt.As already explained at the beginning, there is a significant advantage of the use described that the combination of coarse ceramic matrix material and dispersed fine-particle micropowder results in the possibility of working without a binder, since the fine-particle single-grain component acts virtually as an "in-situ binder".

Um den Dispergiereffekt der feinteiligen Komponente zu optimieren, wird der entsprechende Massenanteil zuvor in einem nicht wässrigen Dispergiermedium aufbereitet (wodurch bei hydratationsempfindlichen Oxiden wie MgO eine Hydratation verhindert wird), wobei das bezüglich des Feststoffs inerte Dispergiermedium zum Beispiel aus Naphtenbasischen Ölen oder Fettalkoholen bestehen kann und als Dispergiermittel zum Beispiel ein modifiziertes Alkydharz (Polyester) eingesetzt wird.In order to optimize the dispersing effect of the finely divided component, the corresponding mass fraction is previously prepared in a non-aqueous dispersing medium (which prevents hydration in the case of hydration-sensitive oxides such as MgO), whereby the dispersing medium which is inert with respect to the solid can consist, for example, of naphthenic oils or fatty alcohols and a modified alkyd resin (polyester) is used as the dispersant, for example.

Das feuerfeste oxidische Mikropulver kann aus unterschiedlichen Oxiden bestehen, beispielsweise MgO, Al₂O₃, Cr₂O₃ und/oder TiO₂. Dabei kann das oxidische Mikropulver lediglich aus einem dieser Oxide bestehen; es ist aber auch möglich, Mischungen dieser Oxide als Mikropulver einzusetzen, insbesondere dann, wenn eine Spinellbildung gewünscht wird. In diesem Fall bietet es sich an, zum Beispiel eine MgO/Cr₂O₃-Dispersion zu verwenden.The refractory oxidic micropowder can consist of different oxides, for example MgO, Al₂O₃, Cr₂O₃ and / or TiO₂. The oxidic micropowder can consist of only one of these oxides; however, it is also possible to use mixtures of these oxides as micropowder, in particular when spinel formation is desired. In this case, it makes sense to use a MgO / Cr₂O₃ dispersion, for example.

Die erfindungsgemäße Verwendung erreicht ihre vorteilhaftesten Eigenschaften dann, wenn eine Dispersion mit einem sehr hohen Feststoffgehalt des oxidischen Mikropulvers eingesetzt wird. Hierunter werden Dispersionen verstanden, die einen Feststoffgehalt von über 85 Gew.-%, bezogen auf die Gesamt-Dispersion, aufweisen. Entsprechend beträgt der Anteil des Dispergierers dann bis zu 15 Gew.-%.The use according to the invention achieves its most advantageous properties when a dispersion with a very high solids content of the oxidic micropowder is used. Dispersions are understood to mean which have a solids content of over 85% by weight, based on the total dispersion. The proportion of the disperser is then up to 15% by weight.

Überraschend wurde festgestellt, daß sich derartige hochkonzentrierte Dispersionen in hochenergiereichen Mischern unter Verwendung eines geeigneten Dispergiermittels (zum Beispiel Polyester) herstellen lassen, wobei der Feststoffanteil sogar auf Werte über 90 Gew.-% eingestellt werden kann.It has surprisingly been found that such highly concentrated dispersions can be prepared in high-energy mixers using a suitable dispersant (for example polyester), and the solids content can even be set to values above 90% by weight.

Das grobkeramische Matrixmaterial wird in Abhängigkeit von den gewünschten Werkstoffeigenschaften ausgewählt.The coarse ceramic matrix material is selected depending on the desired material properties.

So ist es für rein magnesitische Produkte möglich, ein magnesitisches, grobkeramisches Matrixmaterial mit einem MgO-Mikropulver aufzubereiten. Ebenso kann in diesem Fall das Mikropulver beispielsweise aber auch aus einer spinellbildenden MgO/Cr₂O₃- oder MgO/Al₂O₃-Dispersion bestehen.It is possible for purely magnesitic products to process a magnesitic, coarse ceramic matrix material with an MgO micropowder. Likewise, in this case the micropowder can also consist, for example, of a spinel-forming MgO / Cr₂O₃ or MgO / Al₂O₃ dispersion.

Im Fall der Verwendung eines grobkeramischen Matrixmaterials auf Basis Al₂O₃ (zum Beispiel Tonerde, Tabulartonerde, Korund), bietet sich die Verwendung eines Al₂O₃-Mikropulvers an, das beispielsweise aber wieder ganz oder teilweise durch TiO₂ oder ein anderes feuerfestes oxidisches Mikropulver ersetzt werden kann.In the case of the use of a coarse ceramic matrix material based on Al₂O₃ (for example alumina, tabular alumina, corundum), the use of an Al₂O₃ micropowder offers itself, which, however, can be replaced in whole or in part by TiO₂ or another refractory oxidic micropowder.

Auch bei Verwendung von nicht hydratationsempfindlichen Oxiden wie Al₂O₃ sollte dieses vorzugsweise in einem nicht wässrigen Dispergiermedium aufbereitet werden, um den Wassergehalt der aufbereiteten Masse so gering wie möglich zu halten. Die Aufbereitungstechnik mit einem nicht wässrigen Dispergiermedium hat den Vorteil, daß sich die vorstehend genannten ungewöhnlich hohen Feststoff-Konzentrationen der Dispersion leichter erreichen lassen, mit der Folge, daß auf diese Weise nicht nur die Grünstandsfestigkeit der keramischen Masse (nach Vermischen mit dem grobkeramischen Matrixmaterial), sondern auch die Dichte nach dem Brand wesentlich gefördert werden kann.Even when using non-hydration-sensitive oxides such as Al₂O₃, this should preferably be processed in a non-aqueous dispersion medium in order to keep the water content of the processed mass as low as possible. The processing technology with a non-aqueous Dispersing medium has the advantage that the above-mentioned unusually high solid concentrations of the dispersion can be achieved more easily, with the result that in this way not only the green stability of the ceramic mass (after mixing with the coarse ceramic matrix material) but also the density the fire can be significantly promoted.

So können unter Verwendung eines MgO-Mikropulvers in reinmagnesitischen Steinen nach dem Brand Dichten von 3,25 g/cm³ erreicht werden.Using an MgO micropowder in pure magnesite stones, densities of 3.25 g / cm³ can be achieved after firing.

Es ist aber auch möglich, die feuerfeste oxidische Mikropulver-Dispersion vor der Vermischung mit dem grobkeramischen Matrixmaterial wieder von dem zur Aufbereitung verwendeten Dispergiermedium zu trennen, beispielsweise durch Sprühtrocknen oder Gefriertrocknen der Dispersion. Dabei wird das Dispergiermedium entfernt, beispielsweise abgesaugt, so daß sehr feines, reines und oberflächenmodifiziertes Mikropulver hergestellt wird. Dieses Mikropulver kann dann auch in wässrigen Systemen eingesetzt werden.However, it is also possible to separate the refractory oxidic micropowder dispersion again from the dispersion medium used for the preparation, for example by spray drying or freeze-drying the dispersion, before it is mixed with the heavy ceramic matrix material. The dispersing medium is removed, for example suctioned off, so that very fine, pure and surface-modified micropowder is produced. This micropowder can then also be used in aqueous systems.

Versuche haben gezeigt, daß sich aus einer Masse, die 85 Gew.-% grobkeramisches MgO-Matrixmaterial in der Kornfraktion > 1,0 µm und < 3 mm sowie 15 Gew.-% eines zuvor dispergierten, feinteiligen MgO-Mikropulvers mit einer Korngröße von 0,9 µm enthält, Formkörper mit einer Kaltdruckfestigkeit des gepreßten Grünlings von 50 bis 60 N/mm² herstellen lassen, wobei dieser Wert um ein Vielfaches über den Werten der Kaltdruckfestigkeit liegt, die aus dem Stand der Technik bekannt sind.Experiments have shown that a mass consisting of 85% by weight of heavy ceramic MgO matrix material in the grain fraction> 1.0 µm and <3 mm and 15% by weight of a previously dispersed, finely divided MgO micropowder with a grain size of Contains 0.9 µm, moldings with a cold compressive strength of the pressed green body of 50 to 60 N / mm² can be produced, this value being many times higher than the values of the cold compressive strength, which are known from the prior art.

Gleichzeitig werden Dichten erzielt, die oberhalb von 3,15 g/cm³ liegen (wobei diese Werte sowohl für die Grünlinge wie auch für den gebrannten Körper gelten).At the same time, densities are achieved which are above 3.15 g / cm³ (these values apply to both the green compacts and the fired body).

Ein wesentlicher weiterer Vorteil besteht darin, daß die aus der beschriebenen Masse hergestellten Formteile im Brand keiner nennenswerten Schwindung unterliegen.A further significant advantage is that the molded parts produced from the composition described are not subject to any significant shrinkage in the fire.

Claims (17)

Verwendung eines nach Dispergierung in einem nicht wässrigen Dispergiermittel erhaltenen feinteiligen, feuerfesten, oxidischen Mikropulvers weitestgehend einheitlicher Korngröße in einem feuerfesten grobkeramischen Matrixmaterial zur Herstellung von keramischen Massen und Formteilen hoher Grünstandsfestigkeit und hoher Dichte nach einem Brand.Use of a finely divided, refractory, oxidic micropowder obtained after dispersion in a non-aqueous dispersant in a largely uniform grain size in a refractory, coarse-ceramic matrix material for the production of ceramic masses and moldings of high green strength and high density after a fire. Verwendung nach Anspruch 1 mit der Maßgabe, daß das Mikropulver eine Teilchengröße von Weniger als 10 µm aufweist.Use according to claim 1 with the proviso that the micropowder has a particle size of less than 10 µm. Verwendung nach Anspruch 2 mit der Maßgabe, daß das Mikropulver eine Teilchengröße von weniger als 1 µm aufweist.Use according to claim 2 with the proviso that the micropowder has a particle size of less than 1 µm. Verwendung nach einem der Ansprüche 1 bis 3 mit der Maßgabe, daß 90 Gew.-% der Teilchen des Mikropulvers eine maximale Abweichung vom mittleren Teilchendurchmesser des MgO-Mikropulvers von ± 10 % aufweisen.Use according to one of Claims 1 to 3, with the proviso that 90% by weight of the particles of the micropowder have a maximum deviation from the mean particle diameter of the MgO micropowder of ± 10%. Verwendung nach einem der Ansprüche 1 bis 4 mit der Maßgabe, daß der Anteil des Mikropulvers an der Gesamtmischung 5 bis 18 Gew.-% beträgt.Use according to one of claims 1 to 4 with the proviso that the proportion of the micropowder in the total mixture is 5 to 18% by weight. Verwendung nach Anspruch 5 mit der Maßgabe, daß der Anteil des Mikropulvers an der Gesamtmischung 10 bis 15 Gew.-% beträgt.Use according to claim 5 with the proviso that the proportion of the micropowder in the total mixture is 10 to 15% by weight. Verwendung nach einem der Ansprüche 1 bis 6 mit der Maßgabe, daß das grobkeramische Matrixmaterial in einer Kornfraktion < 5 mm und > als das feinteilige Mikropulver vorliegt.Use according to one of claims 1 to 6 with the proviso that the coarse ceramic matrix material is present in a grain fraction <5 mm and> as the finely divided micropowder. Verwendung nach einem der Ansprüche 1 bis 7 mit der Maßgabe, daß die Mischung aus Mikropulver und grobkeramischem Matrixmaterial bindemittelfrei ist.Use according to one of claims 1 to 7, with the proviso that the mixture of micropowder and heavy ceramic matrix material is binder-free. Verwendung nach einem der Ansprüche 1 bis 8 mit der Maßgabe, daß das feinteilige Mikropulver in einem Dispergiermedium auf Basis Naphten-basischen Öls oder Fettalkohol aufbereitet wurde.Use according to one of claims 1 to 8 with the proviso that the finely divided micropowder has been prepared in a dispersing medium based on naphthenic oil or fatty alcohol. Verwendung nach einem der Ansprüche 1 bis 9 mit der Maßgabe, daß ein Mikropulver auf Basis MgO, Al₂O₃, Cr₂O₃ und/oder TiO₂ eingesetzt wird.Use according to one of claims 1 to 9 with the proviso that a micropowder based on MgO, Al₂O₃, Cr₂O₃ and / or TiO₂ is used. Verwendung nach Anspruch 10 mit der Maßgabe, daß als Mikropulver ein spinellbildendes Oxidgemisch eingesetzt wird.Use according to claim 10 with the proviso that a spinel-forming oxide mixture is used as the micropowder. Verwendung nach einem der Ansprüche 1 bis 11 mit der Maßgabe, daß als feuerfestes, grobkeramisches Matrixmaterial MgO, Al₂O₃ und/oder Cr₂O₃ eingesetzt wird.Use according to one of claims 1 to 11 with the proviso that MgO, Al₂O₃ and / or Cr₂O₃ is used as the refractory, coarse ceramic matrix material. Verwendung nach Anspruch 12 mit der Maßgabe, daß ein, mit dem Mikropulver spinellbildendes Oxid als feuerfestes, grobkeramisches Matrixmaterial eingesetzt wird.Use according to claim 12 with the proviso that an oxide which forms spinel with the micropowder is used as the refractory, coarse ceramic matrix material. Verwendung nach einem der Ansprüche 1 bis 13 mit der Maßgabe, daß eine Mikropulver-Dispersion mit einem Feststoffgehalt über 85 Gew.-% eingesetzt wird.Use according to one of claims 1 to 13 with the proviso that a micropowder dispersion with a solids content of over 85% by weight is used. Verwendung nach Anspruch 14 mit der Maßgabe, daß eine Mikropulver-Dispersion mit einem Feststoffgehalt über 90 Gew.-% eingesetzt wird.Use according to claim 14 with the proviso that a micropowder dispersion with a solids content of over 90% by weight is used. Verwendung nach einem der Ansprüche 1 bis 15 mit der Maßgabe, daß die Mikropulver-Dispersion vor der Zugabe (Zumischung) zum grobkeramischen Matrixmaterial einer Behandlung zur Entfernung des Dispergiermediums unterworfen wird.Use according to one of Claims 1 to 15 with the proviso that the micropowder dispersion is subjected to a treatment for removing the dispersing medium before it is added (admixed) to the coarse ceramic matrix material. Verwendung nach Anspruch 16 mit der Maßgabe, daß die Mikropulver-Dispersion vor der Zugabe (Zumischung) zum grobkeramischen Matrixmaterial einer Sprühtrocknung oder Gefriertrocknung unterworfen wird.Use according to claim 16 with the proviso that the micropowder dispersion is subjected to spray drying or freeze drying before being added (admixed) to the coarse ceramic matrix material.
EP93108918A 1992-06-05 1993-06-03 Use of refractory, oxide micropowder for making ceramic masses and bodies Expired - Lifetime EP0573029B1 (en)

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DE4218565 1992-06-05
DE4218565 1992-06-05
DE4237317 1992-11-05
DE4237317 1992-11-05

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EP0573029A3 EP0573029A3 (en) 1994-09-07
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EP (1) EP0573029B1 (en)
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WO2014048586A1 (en) * 2012-09-28 2014-04-03 Refractory Intellectual Property Gmbh & Co. Kg Mix for producing a fire-resistant material, a fire-resistant material, a method for producing a fire-resistant material and use of a material as a sintering aid

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CN102084137B (en) 2009-04-23 2013-10-16 萱场工业株式会社 Pipe securing structure for cylinder tube
CN110981502A (en) * 2020-01-16 2020-04-10 宜兴必方陶瓷科技有限公司 Production method of ceramic bonding agent used in unburned carbon-containing brick process formula

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ATE138055T1 (en) 1996-06-15
EP0573029A3 (en) 1994-09-07
EP0573029B1 (en) 1996-05-15
JPH0656506A (en) 1994-03-01
US5426078A (en) 1995-06-20
DE59302569D1 (en) 1996-06-20
CA2097755C (en) 1997-06-24

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